CMX838 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
Bit(s)
TX SUBAUDIO
LEVEL
Bit 12-8
SUBAUDIO
LOW PASS
FILTER 2 GAIN
Bit 7
SUBAUDIO
FILTER
OUTPUT
ENABLE
Bit 6
DC
RESTORATION
Bit 5
Description
Bit 12
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Bit 11
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Bit 10
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Bit 9
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 8
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Subaudio Gain
Off
-7.5dB
-7.0dB
-6.5dB
-6.0dB
-5.5dB
-5.0dB
-4.5dB
-4.0dB
-3.5dB
-3.0dB
-2.5dB
-2.0dB
-1.5dB
-1.0dB
-0.5dB
0.0dB
0.5dB
1.0dB
1.5dB
2.0dB
2.5dB
3.0dB
3.5dB
4.0dB
4.5dB
5.0dB
5.5dB
6.0dB
6.5dB
7.0dB
7.5dB
Setting to a logic ‘1’ forces 2nd subaudio filter stage to have 0dB gain in LPF mode,
resulting in a Gain boost of 18dB over the normal setting. Used in conjunction with bit
13 this can allow an RX signal path with pass band response down to DC with a
nominal overall pass band gain of 22dB. In normal operation, this bit should be a logic
‘0’.
This bit can be used to expose the Subaudio filter output through the MOD block in RX
mode. Normally the Subaudio filter output is only connected to the MOD block in TX
mode. Setting this bit to a logic ‘1’ connects the filter output to the MOD block in both
TX and RX modes. In normal operation, this bit should be a logic ‘0’.
Set this bit to a logic ‘1’ to enable external DC restore mode. In external DC restore
mode, an external capacitor to ground at the AUX I/O pin is required to compensate for
internal filter offsets. In normal operation, this bit should be a logic ‘0’.
2003 CML Microsystems Plc
44
D/838/8
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